1. Field of the Invention
The present invention relates to a method and device for improving the performance of an antenna, and more particularly, to a method and device for improving the performance of an antenna that communicates in a plurality of bands.
2. Background of the Invention
A wireless communication electronic device has become one of the most essential electronic devices in to people. Especially since communication speed and data processing speed has improved rapidly in recent years, and a User Equipment (UE), such as a smartphone which provides a user functionality beyond web surfing, has formed the mainstream of a wireless communication electronic device.
A wireless communication electronic device essentially includes an antenna in order to perform wireless communication. An antenna for receiving a diversity signal may be realized in the electronic device. However, it is difficult for an electronic device such as a current smartphone to improve diversity radiation performance due to constrains such as an earphone jack at the upper end of the electronic device, a front camera, a rear camera decoration or deco, a receiver, and a front sensor.
Moreover, telecommunications carriers receive a predetermined frequency band in order to provide Long Term Evolution (LTE) service. During this process, due to various strategic/policy reasons, an adjustment to an original frequency band that a telecommunications carrier uses may be made. For example, if an existing LTE Band 3 1700 Channel (CH) (i.e., a center frequency of 1700CH is 1855.0 MHz) frequency band (Down Link (DL) 10 MHz) for LTE Band 3 (B3) service is returned and a LTE B3 1350CH (i.e., a center frequency of 1350CH is 1820.0 MHz) frequency band (DL 20 MHz) is assigned, a band used for LTE B3 service by telecommunications carriers moves to a frequency band that is lower by 35 MHz than before.
However, in this case, a newly extended frequency band may not be covered by the radiation performance of an antenna mounted on an existing electronic device. This is described below with reference to FIG. 1.
FIG. 1 is a graph of a Voltage Standing Wave Ratio (VSWR) of a lower end antenna of a portable terminal. As shown in FIG. 1, an antenna system mounted in a terminal may support LTE B3 and Wideband Code Division Multiple Access (WCDMA) Band 1 (B1) frequency bands. That is, an antenna system is designed to obtain a broadband signal corresponding to 1800 MHz (i.e., LTE B3 band) and 2100 MHz (i.e., WCDMA B1 band). However, when a frequency band that a terminal device supports is changed, as mentioned above, in order to cover 1350CH band in addition to the existing band, while maintaining a bandwidth, a frequency band may need to be moved a frequency band to the left or a bandwidth may need to be extended to the left.
However, extending a bandwidth to the left (i.e., extending a bandwidth to a relatively lower frequency band) while maintaining an existing band may be impossible to do because of the structure of a terminal or an antenna. When a bandwidth moves to the left to satisfy LTE B3 1350CH Total Radiated Power (TRP) performance, it is expected that WCDMA B1 Total Isotropic Sensitivity (TIS) performance will deteriorate.